1. Field of the Invention
The present invention relates to a technique for encoding image data.
2. Description of the Related Art
Conventionally, a technique for performing area separation processing on an image obtained by scanning, generating attribute map information indicating character areas and photographic areas to which each pixel belongs, and setting an image processing parameter in correspondence with the attribute map information, is known (see Japanese Patent Application Laid-Open No. 2006-140970).
In this method, when a pixel is a character pixel, a “1” 1-bit signal is outputted, on the other hand, when the pixel is a photographic pixel, a “0” 1-bit signal is outputted. As a result, edge emphasis processing or the like is performed for character pixels to sharpen a character portion, while smoothing processing is performed for picture pixels. Thus an excellent output image, in which processings corresponding to respective attributes have been performed, can be obtained.
Further, to prevent image degradation in encoding of a mixed image including character and photographic image areas, for example, Japanese Patent Application Laid-Open No. 2002-077633 discloses first separating a character image area (hereinbelow, a “character area”) and a photographic image area (hereinbelow, a “photographic area”), and performing binary lossless encoding processing such as MMR on the character area, while performing JEPG encoding on the other area than the character area, thereby suppressing image degradation in compression-encoding at a high compression rate.
However, in the above method, to perform appropriate image processing by image area, it is necessary to prepare attribute data by each pixel for several bits. This causes a problem in increase in the amount of attribute data. Further, when area separation is performed then encoding is performed, character processing such as edge emphasis is not performed on other areas than a character area. When erroneous determination has occurred, an output image with excellent image quality cannot be obtained.